Definition
Cancer is the uncontrolled growth of abnormal cells in the body. Cancerous cells are also called malignant cells.
Alternative Names
Carcinoma; Malignant tumor
Causes, incidence, and risk factors
Cells are the building blocks of living things. Cancer grows out of normal cells in the body. Normal cells multiply when the body needs them, and die when the body doesn't. Cancer appears to occur when the growth of cells in the body is out of control and cells divide too rapidly. It can also occur when cells “forget” how to die.
There are many different kinds of cancers. Cancer can develop in almost any organ or tissue, such as the lung, colon, breast, skin, bones, or nerve tissue.
There are multiple causes of cancers, including:
- Radiation
- Sunlight
- Tobacco
- Certain viruses
- Benzene
- Certain poisonous mushrooms and aflatoxins (a poison produced by organisms that can grow on peanut plants)
However, the cause of many cancers remains unknown.
The most common cause of cancer-related death is lung cancer.
The three most common cancers in men in the United States are prostate cancer, lung cancer, and colon cancer. In women in the U.S., the three most frequently occurring cancers are breast cancer, lung cancer, and colon cancer.
Certain cancers are more common in particular geographic areas. For example, in Japan, there are many cases of gastric cancer, while in the U.S. this type of cancer is relatively rare.
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